全新java初学者实践教程6(Java SE5.0版)
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~ 基本语法3
-ZaeX]^&Q\ @ZJL]TO ?4b0\ - 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
-Uo11'{ i=gZ8Q=H [font="Times] 1.循环语句[font="Times]:while,do-while,for
,#)d Lk(ESV;r [font="Times]2.分支语句[font="Times]:if-else,switch,
8c9HJ9vk [font="Times]
IXy6Yn9l 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
oqJYbim [font="Times]
EOB8|:* 4.异常处理语句[font="Times]:try-catch-finally,throw
b >D /s4~Ij`be 实践:
%B$ftsYXmu [font="Times] 1.循环语句
RIMSXue*Ha [font="Times] while 语句
yx]9rD1cz [font="Times]class While {
P{o)Ir8Tt [font="Times]public static void main(String args[]) {
^QS`H@+Z [font="Times]int n = 10;
(Q8!5s [font="Times]while(n > 0) {
G8av5zR [font="Times]System.out.println("tick " + n);
2{=]Pf [font="Times]n--;
]E/0iM5 [font="Times]}
1iF=~@Nz_ [font="Times]}
Pe_O( [font="Times]}
"Vp
nr +6 [font="Times] do…while 语句
9B0ON*` [font="Times] class DoWhile {
.!o]oM
U/ [font="Times]public static void main(String args[]) {
4#IT" i [font="Times]int n = 10;
2VN].t: [font="Times]do {
hZJ~zx~ [font="Times]System.out.println("tick " + n);
?EFRf~7JP [font="Times]n--;
G[k3` [font="Times]} while(n > 0);
e0`z~z]6& [font="Times]}
hY&Yp^"}]^ [font="Times]}
q<:8{Y| 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
VVeJe"!t [font="Times] for语句
z.8/[) [font="Times] class ForTick {
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Z%|5(] [font="Times]public static void main(String args[]) {
F vkyp"W3 [font="Times]int n;
wKM9fs [font="Times]for(n=10; n>0; n--)
=|?`5!A [font="Times]System.out.println("tick " + n);
gzs\C{4D [font="Times]}
qX@e+&4P0 [font="Times]}
99=~vNn 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
NH/A`Wm 还有啊,[font="Times]for循环的部分可以为空的
Tx.N#,T| [font="Times]class ForVar {
?#z$(upQ [font="Times]public static void main(String args[]) {
Py; 5z [font="Times]int i;
ve
d]X! [font="Times]boolean done = false;
Q a (Sb [font="Times]i = 0;
+?*;#=q [font="Times]for( ; !done; ) {
cACIy yQ [font="Times]System.out.println("i is " + i);
KL_/f [font="Times]if(i == 10) done = true;
,`HweIq( [font="Times]i++;
R #wZW&N [font="Times]}
n#">k%bD [font="Times]}
*Ypn@YpSp [font="Times]}
循环语句的例子下载 8B GZ [font="Times] 2.分支语句[font="Times]
<wSJK [font="Times] if/else语句
95,]86 [font="Times]class IfElse {
V#ELn[k [font="Times]public static void main(String args[]) {
B'yjMY![
[font="Times]int month = 4; // April
[BE_^d5& [font="Times]String season;
=>
(g_\ [font="Times]if(month == 12 || month == 1 || month == 2)
Q4cCg7|0 [font="Times]season = "Winter";
(l99a&]t [font="Times]else if(month == 3 || month == 4 || month == 5)
DzpWU8j [font="Times]season = "Spring";
e}uK"dl( [font="Times]else if(month == 6 || month == 7 || month == 8)
@AZNF+
\W$ [font="Times]season = "Summer";
yI^Yh{
[font="Times]else if(month == 9 || month == 10 || month == 11)
!,`'VQw$ [font="Times]season = "Autumn";
I/(U0`% [font="Times]else
uz!8=,DFw [font="Times]season = "Bogus Month";
({E,}x [font="Times]System.out.println("April is in the " + season + ".");
u !BU^@ P [font="Times]}
}k }=e [font="Times]}
nYx
/q [font="Times]//这段程序输出[font="Times]:
$\u\4n [font="Times]//April is in the Spring.
63oe0T& [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
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Ej#mk [font="Times] switch语句
k?fz @H8D( [font="Times] class Switch {
j#//U2VdN [font="Times]public static void main(String args[]) {
A]bQUWt2 [font="Times]int month = 4;
%tVU Rj [font="Times]String season;
(,I:m[0 [font="Times]switch (month) {
C'I&< [font="Times]case 12:
sx#O3*'>1 [font="Times]case 1:
76w[X=Fv [font="Times]case 2:
5sJ>+Rg [font="Times]season = "Winter";
;KQU%
k$ [font="Times]break;
":/c|! [font="Times]case 3:
J@-'IJ [font="Times]case 4:
)]fiyXA
[font="Times]case 5:
-YQh
F;/ [font="Times]season = "Spring";
b\"F6TF: [font="Times]break;
6:2* < [font="Times]case 6:
"pO [font="Times]case 7:
{?yVA [font="Times]case 8:
^Gd1T [font="Times]season = "Summer";
d_,My lk [font="Times]break;
O&7.Ry
m [font="Times]case 9:
{"'M2w:|D1 [font="Times]case 10:
4np2I~ ! [font="Times]case 11:
) f~;P+ [font="Times]season = "Autumn";
}`w(sec:3 [font="Times]break;
|m-N5$\IC [font="Times]default:
*y4g\#o. [font="Times]season = "Bogus Month";
OL\-SQ& [font="Times]}
A-r;5?S [font="Times]System.out.println("April is in the " + season + ".");
h ;uzbu [font="Times]}
i431mpMa [font="Times]}
分支语句代码下载 T:Cq}4k< &oG>Rqkm [font="Times]switch语句适合于条件非常多的逻辑
G u`xJ 请看上述语句可以混合使用,请看
下载例子